Location: Siegen, Germany Date: 2011 Industry: Research
The Challenge​
Improving the Pedersen generator to reduce cost and achieve higher accuracy to meet the ExoMars mission requirements.
The solution
Applying lookup table compression and interpolation techniques to improve spectral purity with minimal hardware overhead.
The outcome
Saving millions in research and industrial activities of the scientific payload of the ExoMars rover as well as reducing equipment complexity.

€1.3 billion

ExoMars mission is using Nawatt’s improved sweep generator on the Mars rover in 2020.

Nawatt’s sweep generator research is used by the ESA on its ExoMars rover

Helping the agency discovering the Red Planet’s subsurface
The Challenge

The radar on the Euro-Russian Mars mission will be deployed on the rover to analyze the underground layers seeking life evidence and examining possible methane sources that could lead humanity to one of the greatest discoveries of our age, namely finding the source of this scarce gas which aims to determine if the Red Planet could ever have supported microbial life.

The required frequency bandwidth is around 2.5 GHz starting at 500MHz up to 3 GHz. The radar will allow the rover to scan the subsurface using sweep pulses and to send high resolution data back to earth, so scientists can build 3D images down to a depth of 3 meters. The sweep pulses will also help determine optimal drilling sites and to investigate subsurface water-ice and brine.

Digital sweep (or chirp) signal generators are tricky to build without high spurious effects in the upper part of the band. While the Pedersen implementation provides a digitally controlled phase signal, it suffers from severe spurious harmonic distortion. Many techniques were proposed to lower the distortion effects, but all resulted in hardware complexity and increase in cost.

The Solution

Nawatt collaborated with the Center for Sensor Systems (ZESS) at the University of Siegen to implement a cost-effective solution that meets the ESA’s accuracy and quality figures.

The suggested method utilizes lookup table (LUT) compression techniques in a Pedersen generator to improve high spurious-free dynamic range (SFDR) while keeping memory size lower than all previous methods. The digitally generated sinusoidal waves are based on a piecewise polynomial approximation that is substituted in real-time. The LUT compression is achieved by using high orders of interpolation which also allowed the generator to exceed spectral purity of all previous techniques with minimal hardware overhead.

The hardware implementation achieved extremely high levels of SFDR reaching 97.5 dBc while reducing the total memory size and hardware complexity.

The Outcome
After the withdrawal of NASA from the ExoMars mission, and the consequent reorganization of the ventures, the member states instructed the ESA to prioritize their missions and adjust to the shortfall in funding. The technical contribution that Nawatt provided in collaboration with ZESS allowed the agency to build a cost-effective, yet a higher quality radar to be deployed on the Mars rover mission saving millions in research and industrial activities of the scientific payload. It also helped scientists to reduce the hardware complexity that improved both power consumption and equipment weight giving more room for other subsystems with the same fuel reservoir.
About the Center for Sensor Systems (ZESS)

The Center for Sensor Systems (ZESS) is a central scientific and interdisciplinary research institution of the University of Siegen. Scientists from the engineering and natural sciences work together under one roof. By networking methods knowledge, simulation, software technologies, electronics and mechanics or the corresponding micro-techniques, ZESS forms an interdisciplinary team to take account of the complexity of today’s development processes. For more information, please visit uni-siegen.de/zess.